add custom HTTP client support

jsonrpc2/client.go

@@ -108,8 +108,8 @@ func (c *clientCodec) WriteRequest(r *rpc.Request, param interface{}) error {
 type clientResponse struct {
 	Version string           `json:"jsonrpc"`
 	ID      *uint64          `json:"id"`
-	Result  *json.RawMessage `json:"result"`
-	Error   *Error           `json:"error"`
+	Result  *json.RawMessage `json:"result,omitempty"`
+	Error   *Error           `json:"error,omitempty"`
 }
 
 func (r *clientResponse) reset() {

jsonrpc2/example_test.go

@@ -98,6 +98,19 @@ func Example() {
 	clientHTTP := jsonrpc2.NewHTTPClient("http://" + lnHTTP.Addr().String() + "/rpc")
 	defer clientHTTP.Close()
 
+	// Custom client use HTTP transport.
+	clientCustomHTTP := jsonrpc2.NewCustomHTTPClient(
+		"http://"+lnHTTP.Addr().String()+"/rpc",
+		jsonrpc2.DoerFunc(func(req *http.Request) (*http.Response, error) {
+			// Setup custom HTTP client.
+			client := &http.Client{}
+			// Modify request as needed.
+			req.Header.Set("Content-Type", "application/json-rpc")
+			return client.Do(req)
+		}),
+	)
+	defer clientCustomHTTP.Close()
+
 	var reply int
 
 	// Synchronous call using positional params and TCP.
@@ -126,6 +139,14 @@ func Example() {
 		fmt.Printf("Err1(): code=%d msg=%q data=%v\n", rpcerr.Code, rpcerr.Message, rpcerr.Data)
 	}
 
+	err = clientCustomHTTP.Call("ExampleSvc.Err2", nil, nil)
+	if err == rpc.ErrShutdown || err == io.ErrUnexpectedEOF {
+		fmt.Printf("Err2(): %q\n", err)
+	} else if err != nil {
+		rpcerr := jsonrpc2.ServerError(err)
+		fmt.Printf("Err2(): code=%d msg=%q data=%v\n", rpcerr.Code, rpcerr.Message, rpcerr.Data)
+	}
+
 	err = clientHTTP.Call("ExampleSvc.Err3", nil, nil)
 	if err == rpc.ErrShutdown || err == io.ErrUnexpectedEOF {
 		fmt.Printf("Err3(): %q\n", err)
@@ -139,5 +160,6 @@ func Example() {
 	// SumAll(3,5,-2)=6
 	// MapLen({a:10,b:20,c:30})=3
 	// Err1(): code=-32000 msg="some issue" data=<nil>
+	// Err2(): code=-32603 msg="bad HTTP Status: 415 Unsupported Media Type" data=<nil>
 	// Err3(): code=42 msg="some issue" data=[one two]
 }

jsonrpc2/http.go

@@ -67,8 +67,24 @@ func (h *httpHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	}
 }
 
+// Doer is an interface for doing HTTP requests.
+type Doer interface {
+	Do(req *http.Request) (resp *http.Response, err error)
+}
+
+// The DoerFunc type is an adapter to allow the use of ordinary
+// functions as HTTP clients. If f is a function with the appropriate
+// signature, DoerFunc(f) is a client that calls f.
+type DoerFunc func(req *http.Request) (resp *http.Response, err error)
+
+// DoerFunc calls f(req).
+func (f DoerFunc) Do(req *http.Request) (resp *http.Response, err error) {
+	return f(req)
+}
+
 type httpClientConn struct {
 	url   string
+	doer  Doer
 	ready chan io.ReadCloser
 	body  io.ReadCloser
 }
@@ -98,7 +114,7 @@ func (conn *httpClientConn) Write(buf []byte) (int, error) {
 			req.Header.Add("Content-Type", contentType)
 			req.Header.Add("Accept", contentType)
 			var resp *http.Response
-			resp, err = (&http.Client{}).Do(req)
+			resp, err = conn.doer.Do(req)
 			if err != nil {
 			} else if resp.Header.Get("Content-Type") != contentType {
 				err = fmt.Errorf("bad HTTP Content-Type: %s", resp.Header.Get("Content-Type"))
@@ -134,5 +150,23 @@ func (conn *httpClientConn) Close() error {
 // NewHTTPClient returns a new Client to handle requests to the
 // set of services at the given url.
 func NewHTTPClient(url string) *Client {
-	return NewClient(&httpClientConn{url: url, ready: make(chan io.ReadCloser, 16)})
+	return NewCustomHTTPClient(url, nil)
+}
+
+// NewCustomHTTPClient returns a new Client to handle requests to the
+// set of services at the given url using provided doer (&http.Client{} by
+// default).
+//
+// Use doer to customize HTTP authorization/headers/etc. sent with each
+// request (it method Do() will receive already configured POST request
+// with url, all required headers and body set according to specification).
+func NewCustomHTTPClient(url string, doer Doer) *Client {
+	if doer == nil {
+		doer = &http.Client{}
+	}
+	return NewClient(&httpClientConn{
+		url:   url,
+		doer:  doer,
+		ready: make(chan io.ReadCloser, 16),
+	})
 }